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GLSELECTBUFFER(3G)		 OpenGL Manual		    GLSELECTBUFFER(3G)

NAME
       glSelectBuffer - establish a buffer for selection mode values

C SPECIFICATION
       void glSelectBuffer(GLsizei size, GLuint * buffer);

PARAMETERS
       size
	   Specifies the size of buffer.

       buffer
	   Returns the selection data.

DESCRIPTION
       glSelectBuffer has two arguments: buffer is a pointer to an array of
       unsigned integers, and size indicates the size of the array.  buffer
       returns values from the name stack (see glInitNames(), glLoadName(),
       glPushName()) when the rendering mode is GL_SELECT (see
       glRenderMode()).	 glSelectBuffer must be issued before selection mode
       is enabled, and it must not be issued while the rendering mode is
       GL_SELECT.

       A programmer can use selection to determine which primitives are drawn
       into some region of a window. The region is defined by the current
       modelview and perspective matrices.

       In selection mode, no pixel fragments are produced from rasterization.
       Instead, if a primitive or a raster position intersects the clipping
       volume defined by the viewing frustum and the user-defined clipping
       planes, this primitive causes a selection hit. (With polygons, no hit
       occurs if the polygon is culled.) When a change is made to the name
       stack, or when glRenderMode() is called, a hit record is copied to
       buffer if any hits have occurred since the last such event (name stack
       change or glRenderMode() call). The hit record consists of the number
       of names in the name stack at the time of the event, followed by the
       minimum and maximum depth values of all vertices that hit since the
       previous event, followed by the name stack contents, bottom name first.

       Depth values (which are in the range [0,1]) are multiplied by 2 32 - 1,
       before being placed in the hit record.

       An internal index into buffer is reset to 0 whenever selection mode is
       entered. Each time a hit record is copied into buffer, the index is
       incremented to point to the cell just past the end of the block of
       names\(emthat is, to the next available cell If the hit record is
       larger than the number of remaining locations in buffer, as much data
       as can fit is copied, and the overflow flag is set. If the name stack
       is empty when a hit record is copied, that record consists of 0
       followed by the minimum and maximum depth values.

       To exit selection mode, call glRenderMode() with an argument other than
       GL_SELECT. Whenever glRenderMode() is called while the render mode is
       GL_SELECT, it returns the number of hit records copied to buffer,
       resets the overflow flag and the selection buffer pointer, and
       initializes the name stack to be empty. If the overflow bit was set
       when glRenderMode() was called, a negative hit record count is
       returned.

NOTES
       The contents of buffer is undefined until glRenderMode() is called with
       an argument other than GL_SELECT.

       glBegin()/glEnd() primitives and calls to glRasterPos() can result in
       hits.  glWindowPos() will always generate a selection hit.

ERRORS
       GL_INVALID_VALUE is generated if size is negative.

       GL_INVALID_OPERATION is generated if glSelectBuffer is called while the
       render mode is GL_SELECT, or if glRenderMode() is called with argument
       GL_SELECT before glSelectBuffer is called at least once.

       GL_INVALID_OPERATION is generated if glSelectBuffer is executed between
       the execution of glBegin() and the corresponding execution of glEnd().

ASSOCIATED GETS
       glGet() with argument GL_NAME_STACK_DEPTH

       glGet() with argument GL_SELECTION_BUFFER_SIZE

       glGetPointerv() with argument GL_SELECTION_BUFFER_POINTER

SEE ALSO
       glFeedbackBuffer(), glInitNames(), glLoadName(), glPushName(),
       glRenderMode()

COPYRIGHT
       Copyright © 1991-2006 Silicon Graphics, Inc. This document is licensed
       under the SGI Free Software B License. For details, see
       http://oss.sgi.com/projects/FreeB/.

AUTHORS
       opengl.org

opengl.org			  04/29/2014		    GLSELECTBUFFER(3G)

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